Likely a dumb question but I gotta ask..... is the fan on a computer power supply supposed to be spinning all the time or just when the power supply gets to a certain temperature?

Simple systems run constantly. More complex systems have temperatures sensitive variable speeds, so as to keep the noise and energy consumption down when not needed. But these systems are designed so that if the sensors fail, they switch to full speed (the safer option) to avoid damage.

Not a dumb question a good one! If its a laptop they do stay on almost all the time because if they over heat you get trouble. I have a laptop and a desk top and yes the fan on both of them run all the time. it stays on to maintain a normal temp in the computer and every thing runs smooth!

There are NO dumb Questions!! I am not sure about a laptop, but I have a desktop, and my fan does not come on, only if it is about 90 degrees in here (which only happens if I do not have my air on) or if I am at my computer for 4-5 hours, then it might come on for about 10 minutes or so. My other computer is upstairs and that fan never runs, and never had a problem with either one..Good Luck.

All the time. Mine increases in speed as it gets hotter though, yours might stay at a constant speed.

It all depends on the make and model of power supply. Period.

Hi, I'm no expert, but i have had computers, otherwise known as boxes of frustration, =) ...When mine were new, the fan rarely came on, (i run my laptop and desktop average 12hr/day) as they got older, say into the second yr, or so.. the fan comes on m ore, and stays on longer, if it's really loud, may want to get it checked, could be your fan is 'going'.
otherwise, a desktop can be air blown out, from taking side off, (I unplug mine, then remove fans and blow out with mini compressor).
my laptop I unscrew everything, and remove battery, and what ever other covers there are, and also blow that out, special attention to fan areas.
This quiets them down, b/c to much dust, (or if you smoke, sticky nicotine dust) can clog intake and output of fans.
=)

As was said depends on the PSU but as a rule on a standard base unit the fan runs at a constant speed, some model speed up when needed and some slow down when not - this option is usually available in the systems BIOS or as a panel on the front of the base. If not yours is a standard model and should be spinning constant. If you find that it is making a noise or slowing many a time it just needs a clean, buy a can of compressed air and blow the fan out, take the side off and give the CPU and GRFX card fans a good clean too. A lot of crap can congregate under the motherboard so give that a clean out also. This will help with the overall performance, speed and length of component life.

The Fan on most Desktops run constantly for temperature control. Since Power Supplies gobble up ALOT of heat, the fans are there to keep it from overheating and/or blowing out. CPU Fans have Thermal Sensors that only turn on the fan when the CPU gets to a certain temperature. Exhaust fans (Optional) can keep the motherboard super cool and you will notice the system that runs faster if it is kept cool.

Hope that helps. ^_^

Yes, very very few computer fans ever stop running - most run constantly all the time. The power supply fan should run at a constant speed, but the processor fan or the graphics card fan may run faster if you are doing more power-hungry things on the computer.